9e66e60d1516806bca446c589bd46605416ac5ab
3 * Key exchange protocol
5 * (c) 2001 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Trivial IP Encryption (TrIPE).
12 * TrIPE is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * TrIPE is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with TrIPE; if not, write to the Free Software Foundation,
24 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 /*----- Header files ------------------------------------------------------*/
31 /*----- Brief protocol overview -------------------------------------------*
33 * Let %$G$% be a cyclic group; let %$g$% be a generator of %$G$%, and let
34 * %$q$% be the order of %$G$%; for a key %$K$%, let %$E_K(\cdot)$% denote
35 * application of the symmetric packet protocol to a message; let
36 * %$H(\cdot)$% be the random oracle. Let $\alpha \inr \{0,\ldots,q - 1\}$%
37 * be Alice's private key; let %$a = g^\alpha$% be her public key; let %$b$%
38 * be Bob's public key.
40 * At the beginning of the session, Alice chooses
42 * %$\rho_A \inr \{0, \ldots q - 1\}$%
46 * %$r_A = g^{\rho_A}$% Alice's challenge
47 * %$c_A = H(\cookie{cookie}, r_A)$% Alice's cookie
48 * %$v_A = \rho_A \xor H(\cookie{expected-reply}, a, r_A, r_B, b^{\rho_A})$%
49 * Alice's challenge check value
50 * %$r_B^\alpha = a^{\rho_B}$% Alice's reply
51 * %$K = r_B^{\rho_A} = r_B^{\rho_A} = g^{\rho_A\rho_B}$%
52 * Alice and Bob's shared secret key
53 * %$w_A = H(\cookie{switch-request}, c_A, c_B)$%
54 * Alice's switch request value
55 * %$u_A = H(\cookie{switch-confirm}, c_A, c_B)$%
56 * Alice's switch confirm value
58 * The messages are then:
60 * %$\cookie{kx-pre-challenge}, r_A$%
61 * Initial greeting. In state @KXS_CHAL@.
63 * %$\cookie{kx-challenge}, r_A, c_B, v_A$%
64 * Here's a full challenge for you to answer.
66 * %$\cookie{kx-reply}, r_A, c_B, v_A, E_K(r_B^\alpha))$%
67 * Challenge accpeted: here's the answer. Commit to my challenge. Move
70 * %$\cookie{kx-switch-rq}, c_A, c_B, E_K(r_B^\alpha, w_A))$%
71 * Reply received: here's my reply. Committed; send data; move to
74 * %$\cookie{kx-switch-ok}, E_K(u_A))$%
75 * Switch received. Committed; send data; move to @KXS_SWITCH@.
78 /*----- Static tables -----------------------------------------------------*/
80 static const char *const pkname
[] = {
81 "pre-challenge", "challenge", "reply", "switch-rq", "switch-ok"
84 /*----- Various utilities -------------------------------------------------*/
88 * Arguments: @const keyexch *kx@ = key exchange state
89 * @time_t now@ = current time in seconds
91 * Returns: Whether the challenge in the key-exchange state is still
92 * valid or should be regenerated.
95 #define VALIDP(kx, now) ((now) < (kx)->t_valid)
99 * Arguments: @ghash *h@ = pointer to hash context
100 * @const dhgrp *g@ = pointer to group
101 * @const dhge *Y@ = pointer to group element
105 * Use: Adds the hash of a group element to the context. Corrupts
109 static void hashge(ghash
*h
, const dhgrp
*g
, const dhge
*Y
)
113 buf_init(&b
, buf_t
, sizeof(buf_t
));
114 g
->ops
->stge(g
, &b
, Y
, DHFMT_HASH
);
116 GH_HASH(h
, BBASE(&b
), BLEN(&b
));
119 /* --- @mpmask@ --- *
121 * Arguments: @buf *b@ = output buffer
122 * @const dhgrp *g@ = the group
123 * @const dhsc *x@ = the plaintext scalar
124 * @size_t n@ = the expected size of the plaintext
125 * @gcipher *mgfc@ = mask-generating function to use
126 * @const octet *k@ = pointer to key material
127 * @size_t ksz@ = size of the key
131 * Use: Masks a scalar: returns %$x \xor H(k)$%, so it's a random
132 * oracle thing rather than an encryption thing. Breaks the
133 * output buffer on error.
136 static void mpmask(buf
*b
, const dhgrp
*g
, const dhsc
*x
, size_t n
,
137 const gccipher
*mgfc
, const octet
*k
, size_t ksz
)
142 if ((p
= buf_get(b
, n
)) == 0) return;
143 mgf
= GC_INIT(mgfc
, k
, ksz
);
144 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
145 trace(T_CRYPTO
, "crypto: masking scalar = %s", g
->ops
->scstr(g
, x
));
146 trace_block(T_CRYPTO
, "crypto: masking key", k
, ksz
);
148 if (g
->ops
->stsc(g
, buf_t
, n
, x
)) { buf_break(b
); return; }
149 GC_ENCRYPT(mgf
, buf_t
, p
, n
);
150 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
151 trace_block(T_CRYPTO
, "crypto: scalar plaintext", buf_t
, n
);
152 trace_block(T_CRYPTO
, "crypto: masked ciphertext", p
, n
);
157 /* --- @mpunmask@ --- *
159 * Arguments: @const dhgrp *g@ = the group
160 * @const octet *p@ = pointer to the ciphertext
161 * @size_t n@ = the size of the ciphertext
162 * @gcipher *mgfc@ = mask-generating function to use
163 * @const octet *k@ = pointer to key material
164 * @size_t ksz@ = size of the key
166 * Returns: The decrypted scalar, or null.
168 * Use: Unmasks a scalar.
171 static dhsc
*mpunmask(const dhgrp
*g
, const octet
*p
, size_t n
,
172 const gccipher
*mgfc
, const octet
*k
, size_t ksz
)
177 mgf
= GC_INIT(mgfc
, k
, ksz
);
178 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
179 trace_block(T_CRYPTO
, "crypto: unmasking key", k
, ksz
);
180 trace_block(T_CRYPTO
, "crypto: masked ciphertext", p
, n
);
182 GC_DECRYPT(mgf
, p
, buf_t
, n
);
183 x
= g
->ops
->ldsc(g
, buf_t
, n
);
184 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
185 trace_block(T_CRYPTO
, "crypto: scalar plaintext", buf_t
, n
);
186 trace(T_CRYPTO
, "crypto: unmasked scalar = %s",
187 x ? g
->ops
->scstr(g
, x
) : "<failed>");
193 /* --- @hashcheck@ --- *
195 * Arguments: @keyexch *kx@ = pointer to key-exchange block
196 * @const dhge *K@ = sender's public key
197 * @const dhge *CC@ = receiver's challenge
198 * @const dhge *C@ = sender's challenge
199 * @const dhge *Y@ = reply to sender's challenge
201 * Returns: Pointer to the hash value (in @buf_t@)
203 * Use: Computes the check-value hash, used to mask or unmask
204 * indices to prove the validity of challenges. This computes
205 * the masking key used in challenge check values. This is
206 * really the heart of the whole thing, since it ensures that
207 * the scalar can be recovered from the history of hashing
208 * queries, which gives us (a) a proof that the authentication
209 * process is zero-knowledge, and (b) a proof that the whole
210 * key-exchange is deniable.
213 static const octet
*hashcheck(keyexch
*kx
, const dhge
*K
,
214 const dhge
*CC
, const dhge
*C
, const dhge
*Y
)
216 ghash
*h
= GH_INIT(kx
->kpriv
->algs
.h
);
217 const dhgrp
*g
= kx
->kpriv
->grp
;
219 HASH_STRING(h
, "tripe-expected-reply");
225 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
226 trace(T_CRYPTO
, "crypto: computing challenge check hash");
227 trace(T_CRYPTO
, "crypto: public key = %s", g
->ops
->gestr(g
, K
));
228 trace(T_CRYPTO
, "crypto: receiver challenge = %s", g
->ops
->gestr(g
, CC
));
229 trace(T_CRYPTO
, "crypto: sender challenge = %s", g
->ops
->gestr(g
, C
));
230 trace(T_CRYPTO
, "crypto: sender reply = %s", g
->ops
->gestr(g
, Y
));
231 trace_block(T_CRYPTO
, "crypto: hash output", buf_t
, kx
->kpriv
->algs
.hashsz
);
237 /* --- @sendchallenge@ --- *
239 * Arguments: @keyexch *kx@ = pointer to key exchange block
240 * @buf *b@ = output buffer for challenge
241 * @const dhge *C@ = peer's actual challenge
242 * @const octet *hc@ = peer's challenge cookie
246 * Use: Writes a full challenge to the message buffer.
249 static void sendchallenge(keyexch
*kx
, buf
*b
,
250 const dhge
*C
, const octet
*hc
)
252 const dhgrp
*g
= kx
->kpriv
->grp
;
253 g
->ops
->stge(g
, b
, kx
->C
, DHFMT_VAR
);
254 buf_put(b
, hc
, kx
->kpriv
->algs
.hashsz
);
255 mpmask(b
, g
, kx
->a
, g
->scsz
, kx
->kpriv
->algs
.mgf
,
256 hashcheck(kx
, kx
->kpriv
->K
, C
, kx
->C
, kx
->RX
),
257 kx
->kpriv
->algs
.hashsz
);
262 * Arguments: @struct timeval *tv@ = the current time
263 * @void *v@ = pointer to key exchange context
267 * Use: Acts when the key exchange timer goes off.
270 static void timer(struct timeval
*tv
, void *v
)
274 T( trace(T_KEYEXCH
, "keyexch: timer has popped"); )
278 /* --- @settimer@ --- *
280 * Arguments: @keyexch *kx@ = pointer to key exchange context
281 * @struct timeval *tv@ = when to set the timer for
285 * Use: Sets the timer for the next key exchange attempt.
288 static void settimer(keyexch
*kx
, struct timeval
*tv
)
290 if (kx
->f
& KXF_TIMER
) sel_rmtimer(&kx
->t
);
291 sel_addtimer(&sel
, &kx
->t
, tv
, timer
, kx
);
297 * Arguments: @struct timeval *tv@ = where to write the timeval
298 * @double t@ = a time as a floating point number
302 * Use: Converts a floating-point time into a timeval.
305 static void f2tv(struct timeval
*tv
, double t
)
308 tv
->tv_usec
= (t
- tv
->tv_sec
)*MILLION
;
311 /* --- @wobble@ --- *
313 * Arguments: @double t@ = a time interval
315 * Returns: The same time interval, with a random error applied.
318 static double wobble(double t
)
320 uint32 r
= rand_global
.ops
->word(&rand_global
);
321 double w
= (r
/F_2P32
) - 0.5;
322 return (t
+ t
*w
*T_WOBBLE
);
325 /* --- @rs_time@ --- *
327 * Arguments: @retry *rs@ = current retry state
328 * @struct timeval *tv@ = where to write the result
329 * @const struct timeval *now@ = current time, or null
333 * Use: Computes a time at which to retry sending a key-exchange
334 * packet. This algorithm is subject to change, but it's
335 * currently a capped exponential backoff, slightly randomized
336 * to try to keep clients from hammering a server that's only
339 * If @now@ is null then the function works out the time for
343 static void rs_time(retry
*rs
, struct timeval
*tv
, const struct timeval
*now
)
352 if (t
> MIN(5)) t
= MIN(5);
360 f2tv(&rtv
, wobble(t
));
361 TV_ADD(tv
, now
, &rtv
);
364 /* --- @retry_reset@ --- *
366 * Arguments: @retry *rs@ = retry state
370 * Use: Resets a retry state to indicate that progress has been
371 * made. Also useful for initializing the state in the first
375 static void rs_reset(retry
*rs
) { rs
->t
= 0; }
377 /*----- Challenge management ----------------------------------------------*/
379 /* --- Notes on challenge management --- *
381 * We may get multiple different replies to our key exchange; some will be
382 * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges
383 * received will be added to the table and given a full response. After
384 * @KX_THRESH@ distinct challenges are received, we return only a `cookie':
385 * our existing challenge, followed by a hash of the sender's challenge. We
386 * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All
387 * properly-formed cookies are assigned a table slot: if none is spare, a
388 * used slot is randomly selected and destroyed. A cookie always receives a
392 /* --- @kxc_destroy@ --- *
394 * Arguments: @kxchal *kxc@ = pointer to the challenge block
398 * Use: Disposes of a challenge block.
401 static void kxc_destroy(kxchal
*kxc
)
403 const dhgrp
*g
= kxc
->kx
->kpriv
->grp
;
404 if (kxc
->f
& KXF_TIMER
)
405 sel_rmtimer(&kxc
->t
);
406 g
->ops
->freege(g
, kxc
->C
);
407 g
->ops
->freege(g
, kxc
->R
);
412 /* --- @kxc_stoptimer@ --- *
414 * Arguments: @kxchal *kxc@ = pointer to the challenge block
418 * Use: Stops the challenge's retry timer from sending messages.
419 * Useful when the state machine is in the endgame of the
423 static void kxc_stoptimer(kxchal
*kxc
)
425 if (kxc
->f
& KXF_TIMER
)
426 sel_rmtimer(&kxc
->t
);
427 kxc
->f
&= ~KXF_TIMER
;
430 /* --- @kxc_new@ --- *
432 * Arguments: @keyexch *kx@ = pointer to key exchange block
434 * Returns: A pointer to the challenge block.
436 * Use: Returns a pointer to a new challenge block to fill in.
437 * In particular, the @c@ and @r@ members are left
441 static kxchal
*kxc_new(keyexch
*kx
)
446 /* --- If we're over reply threshold, discard one at random --- */
448 if (kx
->nr
< KX_NCHAL
)
451 i
= rand_global
.ops
->range(&rand_global
, KX_NCHAL
);
452 kxc_destroy(kx
->r
[i
]);
455 /* --- Fill in the new structure --- */
457 kxc
= CREATE(kxchal
);
466 /* --- @kxc_bychal@ --- *
468 * Arguments: @keyexch *kx@ = pointer to key exchange block
469 * @const dhge *C@ = challenge from remote host
471 * Returns: Pointer to the challenge block, or null.
473 * Use: Finds a challenge block, given its challenge.
476 static kxchal
*kxc_bychal(keyexch
*kx
, const dhge
*C
)
478 const dhgrp
*g
= kx
->kpriv
->grp
;
481 for (i
= 0; i
< kx
->nr
; i
++) {
482 if (g
->ops
->eq(g
, C
, kx
->r
[i
]->C
))
488 /* --- @kxc_byhc@ --- *
490 * Arguments: @keyexch *kx@ = pointer to key exchange block
491 * @const octet *hc@ = challenge hash from remote host
493 * Returns: Pointer to the challenge block, or null.
495 * Use: Finds a challenge block, given a hash of its challenge.
498 static kxchal
*kxc_byhc(keyexch
*kx
, const octet
*hc
)
502 for (i
= 0; i
< kx
->nr
; i
++) {
503 if (memcmp(hc
, kx
->r
[i
]->hc
, kx
->kpriv
->algs
.hashsz
) == 0)
509 /* --- @kxc_answer@ --- *
511 * Arguments: @keyexch *kx@ = pointer to key exchange block
512 * @kxchal *kxc@ = pointer to challenge block
516 * Use: Sends a reply to the remote host, according to the data in
517 * this challenge block.
520 static void kxc_answer(keyexch
*kx
, kxchal
*kxc
);
522 static void kxc_timer(struct timeval
*tv
, void *v
)
525 kxc
->f
&= ~KXF_TIMER
;
526 kxc_answer(kxc
->kx
, kxc
);
529 static void kxc_answer(keyexch
*kx
, kxchal
*kxc
)
531 stats
*st
= p_stats(kx
->p
);
532 buf
*b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_REPLY
);
533 const dhgrp
*g
= kx
->kpriv
->grp
;
537 /* --- Build the reply packet --- */
539 T( trace(T_KEYEXCH
, "keyexch: sending reply to `%s'", p_name(kx
->p
)); )
540 sendchallenge(kx
, b
, kxc
->C
, kxc
->hc
);
541 buf_init(&bb
, buf_i
, sizeof(buf_i
));
542 g
->ops
->stge(g
, &bb
, kxc
->R
, DHFMT_STD
);
544 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_REPLY
, &bb
, b
);
546 /* --- Update the statistics --- */
550 st
->sz_kxout
+= BLEN(b
);
554 /* --- Schedule another resend --- */
556 if (kxc
->f
& KXF_TIMER
)
557 sel_rmtimer(&kxc
->t
);
558 gettimeofday(&tv
, 0);
559 rs_time(&kxc
->rs
, &tv
, &tv
);
560 sel_addtimer(&sel
, &kxc
->t
, &tv
, kxc_timer
, kxc
);
564 /*----- Individual message handlers ---------------------------------------*/
566 /* --- @doprechallenge@ --- *
568 * Arguments: @keyexch *kx@ = pointer to key exchange block
569 * @buf *b@ = buffer containing the packet
571 * Returns: Zero if OK, nonzero of the packet was rejected.
573 * Use: Processes a pre-challenge message.
576 static int doprechallenge(keyexch
*kx
, buf
*b
)
578 stats
*st
= p_stats(kx
->p
);
579 const dhgrp
*g
= kx
->kpriv
->grp
;
583 /* --- Ensure that we're in a sensible state --- */
585 if (kx
->s
!= KXS_CHAL
) {
586 a_warn("KX", "?PEER", kx
->p
, "unexpected", "pre-challenge", A_END
);
590 /* --- Unpack the packet --- */
592 if ((C
= g
->ops
->ldge(g
, b
, DHFMT_VAR
)) == 0 || BLEFT(b
))
595 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
596 trace(T_CRYPTO
, "crypto: challenge = %s", g
->ops
->gestr(g
, C
));
599 /* --- Send out a full challenge by return --- */
601 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_CHAL
);
602 h
= GH_INIT(kx
->kpriv
->algs
.h
);
603 HASH_STRING(h
, "tripe-cookie");
605 sendchallenge(kx
, b
, C
, GH_DONE(h
, 0));
608 st
->sz_kxout
+= BLEN(b
);
613 g
->ops
->freege(g
, C
);
617 if (C
) g
->ops
->freege(g
, C
);
621 /* --- @respond@ --- *
623 * Arguments: @keyexch *kx@ = pointer to key exchange block
624 * @unsigned msg@ = message code for this packet
625 * @buf *b@ = buffer containing the packet
627 * Returns: Key-exchange challenge block, or null.
629 * Use: Computes a response for the given challenge, entering it into
630 * a challenge block and so on.
633 static kxchal
*respond(keyexch
*kx
, unsigned msg
, buf
*b
)
635 const dhgrp
*g
= kx
->kpriv
->grp
;
636 const algswitch
*algs
= &kx
->kpriv
->algs
;
637 size_t ixsz
= g
->scsz
;
641 const octet
*hc
, *ck
;
649 /* --- Unpack the packet --- */
651 if ((C
= g
->ops
->ldge(g
, b
, DHFMT_VAR
)) == 0 ||
652 (hc
= buf_get(b
, algs
->hashsz
)) == 0 ||
653 (ck
= buf_get(b
, ixsz
)) == 0) {
654 a_warn("KX", "?PEER", kx
->p
, "invalid", "%s", pkname
[msg
], A_END
);
657 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
658 trace(T_CRYPTO
, "crypto: challenge = %s", g
->ops
->gestr(g
, C
));
659 trace_block(T_CRYPTO
, "crypto: cookie", hc
, algs
->hashsz
);
660 trace_block(T_CRYPTO
, "crypto: check-value", ck
, ixsz
);
663 /* --- Discard a packet with an invalid cookie --- */
665 if (hc
&& memcmp(hc
, kx
->hc
, algs
->hashsz
) != 0) {
666 a_warn("KX", "?PEER", kx
->p
, "incorrect", "cookie", A_END
);
670 /* --- Recover the check value and verify it --- *
672 * To avoid recomputation on replays, we store a hash of the `right'
673 * value. The `correct' value is unique, so this is right.
675 * This will also find a challenge block and, if necessary, populate it.
678 if ((kxc
= kxc_bychal(kx
, C
)) != 0) {
679 h
= GH_INIT(algs
->h
);
680 HASH_STRING(h
, "tripe-check-hash");
681 GH_HASH(h
, ck
, ixsz
);
682 ok
= !memcmp(kxc
->ck
, GH_DONE(h
, 0), algs
->hashsz
);
684 if (!ok
) goto badcheck
;
687 /* --- Compute the reply, and check the magic --- */
689 R
= g
->ops
->mul(g
, kx
->kpriv
->k
, C
);
690 if ((c
= mpunmask(g
, ck
, ixsz
, algs
->mgf
,
691 hashcheck(kx
, kx
->kpub
->K
, kx
->C
, C
, R
),
694 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
695 trace(T_CRYPTO
, "crypto: computed reply = %s", g
->ops
->gestr(g
, R
));
696 trace(T_CRYPTO
, "crypto: recovered log = %s", g
->ops
->scstr(g
, c
));
698 CC
= g
->ops
->mul(g
, c
, 0);
699 if (!g
->ops
->eq(g
, CC
, C
)) goto badcheck
;
701 /* --- Fill in a new challenge block --- */
707 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-check-hash");
708 GH_HASH(h
, ck
, ixsz
);
709 GH_DONE(h
, kxc
->ck
); GH_DESTROY(h
);
711 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-cookie");
712 hashge(h
, g
, kxc
->C
);
713 GH_DONE(h
, kxc
->hc
); GH_DESTROY(h
);
715 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
716 trace_block(T_CRYPTO
, "crypto: computed cookie",
717 kxc
->hc
, algs
->hashsz
);
720 /* --- Work out the shared key --- */
722 R
= g
->ops
->mul(g
, kx
->a
, kxc
->C
);
723 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
724 trace(T_CRYPTO
, "crypto: shared secret = %s", g
->ops
->gestr(g
, R
));
727 /* --- Compute the switch messages --- */
729 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-switch-request");
730 hashge(h
, g
, kx
->C
); hashge(h
, g
, kxc
->C
);
731 GH_DONE(h
, kxc
->hswrq_out
); GH_DESTROY(h
);
732 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-switch-confirm");
733 hashge(h
, g
, kx
->C
); hashge(h
, g
, kxc
->C
);
734 GH_DONE(h
, kxc
->hswok_out
); GH_DESTROY(h
);
736 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-switch-request");
737 hashge(h
, g
, kxc
->C
); hashge(h
, g
, kx
->C
);
738 GH_DONE(h
, kxc
->hswrq_in
); GH_DESTROY(h
);
739 h
= GH_INIT(algs
->h
); HASH_STRING(h
, "tripe-switch-confirm");
740 hashge(h
, g
, kxc
->C
); hashge(h
, g
, kx
->C
);
741 GH_DONE(h
, kxc
->hswok_in
); GH_DESTROY(h
);
743 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
744 trace_block(T_CRYPTO
, "crypto: outbound switch request",
745 kxc
->hswrq_out
, algs
->hashsz
);
746 trace_block(T_CRYPTO
, "crypto: outbound switch confirm",
747 kxc
->hswok_out
, algs
->hashsz
);
748 trace_block(T_CRYPTO
, "crypto: inbound switch request",
749 kxc
->hswrq_in
, algs
->hashsz
);
750 trace_block(T_CRYPTO
, "crypto: inbound switch confirm",
751 kxc
->hswok_in
, algs
->hashsz
);
754 /* --- Create a new symmetric keyset --- */
756 buf_init(&bb
, buf_o
, sizeof(buf_o
));
757 g
->ops
->stge(g
, &bb
, kx
->C
, DHFMT_HASH
); x
= BLEN(&bb
);
758 g
->ops
->stge(g
, &bb
, kxc
->C
, DHFMT_HASH
); y
= BLEN(&bb
);
759 g
->ops
->stge(g
, &bb
, R
, DHFMT_HASH
); z
= BLEN(&bb
);
762 kxc
->ks
= ks_gen(BBASE(&bb
), x
, y
, z
, kx
->p
);
765 if (C
) g
->ops
->freege(g
, C
);
766 if (CC
) g
->ops
->freege(g
, CC
);
767 if (R
) g
->ops
->freege(g
, R
);
768 if (c
) g
->ops
->freesc(g
, c
);
772 a_warn("KX", "?PEER", kx
->p
, "bad-expected-reply-log", A_END
);
775 if (C
) g
->ops
->freege(g
, C
);
776 if (CC
) g
->ops
->freege(g
, CC
);
777 if (R
) g
->ops
->freege(g
, R
);
778 if (c
) g
->ops
->freesc(g
, c
);
782 /* --- @dochallenge@ --- *
784 * Arguments: @keyexch *kx@ = pointer to key exchange block
785 * @unsigned msg@ = message code for the packet
786 * @buf *b@ = buffer containing the packet
788 * Returns: Zero if OK, nonzero if the packet was rejected.
790 * Use: Processes a packet containing a challenge.
793 static int dochallenge(keyexch
*kx
, buf
*b
)
797 if (kx
->s
!= KXS_CHAL
) {
798 a_warn("KX", "?PEER", kx
->p
, "unexpected", "challenge", A_END
);
801 if ((kxc
= respond(kx
, KX_CHAL
, b
)) == 0)
804 a_warn("KX", "?PEER", kx
->p
, "invalid", "challenge", A_END
);
814 /* --- @resend@ --- *
816 * Arguments: @keyexch *kx@ = pointer to key exchange context
820 * Use: Sends the next message for a key exchange.
823 static void resend(keyexch
*kx
)
827 stats
*st
= p_stats(kx
->p
);
829 const dhgrp
*g
= kx
->kpriv
->grp
;
834 T( trace(T_KEYEXCH
, "keyexch: sending prechallenge to `%s'",
836 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_PRECHAL
);
837 g
->ops
->stge(g
, b
, kx
->C
, DHFMT_VAR
);
840 T( trace(T_KEYEXCH
, "keyexch: sending switch request to `%s'",
843 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCH
);
844 buf_put(b
, kx
->hc
, kx
->kpriv
->algs
.hashsz
);
845 buf_put(b
, kxc
->hc
, kx
->kpriv
->algs
.hashsz
);
846 buf_init(&bb
, buf_i
, sizeof(buf_i
));
847 g
->ops
->stge(g
, &bb
, kxc
->R
, DHFMT_STD
);
848 buf_put(&bb
, kxc
->hswrq_out
, kx
->kpriv
->algs
.hashsz
);
850 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCH
, &bb
, b
);
853 T( trace(T_KEYEXCH
, "keyexch: sending switch confirmation to `%s'",
856 b
= p_txstart(kx
->p
, MSG_KEYEXCH
| KX_SWITCHOK
);
857 buf_init(&bb
, buf_i
, sizeof(buf_i
));
858 buf_put(&bb
, kxc
->hswok_out
, kx
->kpriv
->algs
.hashsz
);
860 ks_encrypt(kxc
->ks
, MSG_KEYEXCH
| KX_SWITCHOK
, &bb
, b
);
868 st
->sz_kxout
+= BLEN(b
);
872 if (kx
->s
< KXS_SWITCH
) {
873 rs_time(&kx
->rs
, &tv
, 0);
878 /* --- @decryptrest@ --- *
880 * Arguments: @keyexch *kx@ = pointer to key exchange context
881 * @kxchal *kxc@ = pointer to challenge block
882 * @unsigned msg@ = type of incoming message
883 * @buf *b@ = encrypted remainder of the packet
885 * Returns: Zero if OK, nonzero on some kind of error.
887 * Use: Decrypts the remainder of the packet, and points @b@ at the
888 * recovered plaintext.
891 static int decryptrest(keyexch
*kx
, kxchal
*kxc
, unsigned msg
, buf
*b
)
895 buf_init(&bb
, buf_o
, sizeof(buf_o
));
896 if (ks_decrypt(kxc
->ks
, MSG_KEYEXCH
| msg
, b
, &bb
)) {
897 a_warn("KX", "?PEER", kx
->p
, "decrypt-failed", "%s", pkname
[msg
], A_END
);
900 if (!BOK(&bb
)) return (-1);
901 buf_init(b
, BBASE(&bb
), BLEN(&bb
));
905 /* --- @checkresponse@ --- *
907 * Arguments: @keyexch *kx@ = pointer to key exchange context
908 * @unsigned msg@ = type of incoming message
909 * @buf *b@ = decrypted remainder of the packet
911 * Returns: Zero if OK, nonzero on some kind of error.
913 * Use: Checks a reply or switch packet, ensuring that its response
917 static int checkresponse(keyexch
*kx
, unsigned msg
, buf
*b
)
919 const dhgrp
*g
= kx
->kpriv
->grp
;
922 if ((R
= g
->ops
->ldge(g
, b
, DHFMT_STD
)) == 0) {
923 a_warn("KX", "?PEER", kx
->p
, "invalid", "%s", pkname
[msg
], A_END
);
926 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
927 trace(T_CRYPTO
, "crypto: reply = %s", g
->ops
->gestr(g
, R
));
929 if (!g
->ops
->eq(g
, R
, kx
->RX
)) {
930 a_warn("KX", "?PEER", kx
->p
, "incorrect", "response", A_END
);
934 g
->ops
->freege(g
, R
);
938 if (R
) g
->ops
->freege(g
, R
);
942 /* --- @commit@ --- *
944 * Arguments: @keyexch *kx@ = pointer to key exchange context
945 * @kxchal *kxc@ = pointer to challenge to commit to
949 * Use: Commits to a particular challenge as being the `right' one,
950 * since a reply has arrived for it.
953 static void commit(keyexch
*kx
, kxchal
*kxc
)
957 for (i
= 0; i
< kx
->nr
; i
++) {
959 kxc_destroy(kx
->r
[i
]);
964 ksl_link(kx
->ks
, kxc
->ks
);
967 /* --- @doreply@ --- *
969 * Arguments: @keyexch *kx@ = pointer to key exchange context
970 * @buf *b@ = buffer containing packet
972 * Returns: Zero if OK, nonzero if the packet was rejected.
974 * Use: Handles a reply packet. This doesn't handle the various
975 * switch packets: they're rather too different.
978 static int doreply(keyexch
*kx
, buf
*b
)
982 if (kx
->s
!= KXS_CHAL
&& kx
->s
!= KXS_COMMIT
) {
983 a_warn("KX", "?PEER", kx
->p
, "unexpected", "reply", A_END
);
986 if ((kxc
= respond(kx
, KX_REPLY
, b
)) == 0 ||
987 decryptrest(kx
, kxc
, KX_REPLY
, b
) ||
988 checkresponse(kx
, KX_REPLY
, b
))
991 a_warn("KX", "?PEER", kx
->p
, "invalid", "reply", A_END
);
994 if (kx
->s
== KXS_CHAL
) {
1005 /* --- @kxfinish@ --- *
1007 * Arguments: @keyexch *kx@ = pointer to key exchange block
1011 * Use: Sets everything up following a successful key exchange.
1014 static void kxfinish(keyexch
*kx
)
1016 kxchal
*kxc
= kx
->r
[0];
1017 struct timeval now
, tv
;
1019 ks_activate(kxc
->ks
);
1020 gettimeofday(&now
, 0);
1021 f2tv(&tv
, wobble(T_REGEN
));
1022 TV_ADD(&tv
, &now
, &tv
);
1025 a_notify("KXDONE", "?PEER", kx
->p
, A_END
);
1026 p_stats(kx
->p
)->t_kx
= time(0);
1029 /* --- @doswitch@ --- *
1031 * Arguments: @keyexch *kx@ = pointer to key exchange block
1032 * @buf *b@ = pointer to buffer containing packet
1034 * Returns: Zero if OK, nonzero if the packet was rejected.
1036 * Use: Handles a reply with a switch request bolted onto it.
1039 static int doswitch(keyexch
*kx
, buf
*b
)
1041 size_t hsz
= kx
->kpriv
->algs
.hashsz
;
1042 const octet
*hc_in
, *hc_out
, *hswrq
;
1045 if ((hc_in
= buf_get(b
, hsz
)) == 0 ||
1046 (hc_out
= buf_get(b
, hsz
)) == 0) {
1047 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-rq", A_END
);
1050 IF_TRACING(T_KEYEXCH
, IF_TRACING(T_CRYPTO
, {
1051 trace_block(T_CRYPTO
, "crypto: challenge", hc_in
, hsz
);
1052 trace_block(T_CRYPTO
, "crypto: cookie", hc_out
, hsz
);
1054 if ((kxc
= kxc_byhc(kx
, hc_in
)) == 0 ||
1055 memcmp(hc_out
, kx
->hc
, hsz
) != 0) {
1056 a_warn("KX", "?PEER", kx
->p
, "incorrect", "switch-rq", A_END
);
1059 if (decryptrest(kx
, kxc
, KX_SWITCH
, b
) ||
1060 checkresponse(kx
, KX_SWITCH
, b
))
1062 if ((hswrq
= buf_get(b
, hsz
)) == 0 || BLEFT(b
)) {
1063 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-rq", A_END
);
1066 IF_TRACING(T_KEYEXCH
, {
1067 trace_block(T_CRYPTO
, "crypto: switch request hash", hswrq
, hsz
);
1069 if (memcmp(hswrq
, kxc
->hswrq_in
, hsz
) != 0) {
1070 a_warn("KX", "?PEER", kx
->p
, "incorrect", "switch-rq", A_END
);
1073 if (kx
->s
== KXS_CHAL
)
1075 if (kx
->s
< KXS_SWITCH
)
1084 /* --- @doswitchok@ --- *
1086 * Arguments: @keyexch *kx@ = pointer to key exchange block
1087 * @buf *b@ = pointer to buffer containing packet
1089 * Returns: Zero if OK, nonzero if the packet was rejected.
1091 * Use: Handles a reply with a switch request bolted onto it.
1094 static int doswitchok(keyexch
*kx
, buf
*b
)
1096 size_t hsz
= kx
->kpriv
->algs
.hashsz
;
1101 if (kx
->s
< KXS_COMMIT
) {
1102 a_warn("KX", "?PEER", kx
->p
, "unexpected", "switch-ok", A_END
);
1106 buf_init(&bb
, buf_o
, sizeof(buf_o
));
1107 if (decryptrest(kx
, kxc
, KX_SWITCHOK
, b
))
1109 if ((hswok
= buf_get(b
, hsz
)) == 0 || BLEFT(b
)) {
1110 a_warn("KX", "?PEER", kx
->p
, "invalid", "switch-ok", A_END
);
1113 IF_TRACING(T_KEYEXCH
, {
1114 trace_block(T_CRYPTO
, "crypto: switch confirmation hash",
1117 if (memcmp(hswok
, kxc
->hswok_in
, hsz
) != 0) {
1118 a_warn("KX", "?PEER", kx
->p
, "incorrect", "switch-ok", A_END
);
1121 if (kx
->s
< KXS_SWITCH
)
1129 /*----- Main code ---------------------------------------------------------*/
1133 * Arguments: @keyexch *kx@ = pointer to key exchange context
1137 * Use: Stops a key exchange dead in its tracks. Throws away all of
1138 * the context information. The context is left in an
1139 * inconsistent state. The only functions which understand this
1140 * state are @kx_free@ and @kx_init@ (which cause it internally
1141 * it), and @start@ (which expects it to be the prevailing
1145 static void stop(keyexch
*kx
)
1147 const dhgrp
*g
= kx
->kpriv
->grp
;
1150 if (kx
->f
& KXF_DEAD
)
1153 if (kx
->f
& KXF_TIMER
)
1154 sel_rmtimer(&kx
->t
);
1155 for (i
= 0; i
< kx
->nr
; i
++)
1156 kxc_destroy(kx
->r
[i
]);
1157 g
->ops
->freesc(g
, kx
->a
);
1158 g
->ops
->freege(g
, kx
->C
);
1159 g
->ops
->freege(g
, kx
->RX
);
1162 kx
->f
&= ~KXF_TIMER
;
1165 /* --- @start@ --- *
1167 * Arguments: @keyexch *kx@ = pointer to key exchange context
1168 * @time_t now@ = the current time
1172 * Use: Starts a new key exchange with the peer. The context must be
1173 * in the bizarre state left by @stop@ or @kx_init@.
1176 static void start(keyexch
*kx
, time_t now
)
1178 algswitch
*algs
= &kx
->kpriv
->algs
;
1179 const dhgrp
*g
= kx
->kpriv
->grp
;
1182 assert(kx
->f
& KXF_DEAD
);
1184 kx
->f
&= ~(KXF_DEAD
| KXF_CORK
);
1186 kx
->a
= g
->ops
->randsc(g
);
1187 kx
->C
= g
->ops
->mul(g
, kx
->a
, 0);
1188 kx
->RX
= g
->ops
->mul(g
, kx
->a
, kx
->kpub
->K
);
1190 kx
->t_valid
= now
+ T_VALID
;
1192 h
= GH_INIT(algs
->h
);
1193 HASH_STRING(h
, "tripe-cookie");
1194 hashge(h
, g
, kx
->C
);
1198 IF_TRACING(T_KEYEXCH
, {
1199 trace(T_KEYEXCH
, "keyexch: creating new challenge");
1200 IF_TRACING(T_CRYPTO
, {
1201 trace(T_CRYPTO
, "crypto: secret = %s", g
->ops
->scstr(g
, kx
->a
));
1202 trace(T_CRYPTO
, "crypto: challenge = %s", g
->ops
->gestr(g
, kx
->C
));
1203 trace(T_CRYPTO
, "crypto: expected response = %s",
1204 g
->ops
->gestr(g
, kx
->RX
));
1205 trace_block(T_CRYPTO
, "crypto: challenge cookie",
1206 kx
->hc
, algs
->hashsz
);
1211 /* --- @checkpub@ --- *
1213 * Arguments: @keyexch *kx@ = pointer to key exchange context
1215 * Returns: Zero if OK, nonzero if the peer's public key has expired.
1217 * Use: Deactivates the key-exchange until the peer acquires a new
1221 static int checkpub(keyexch
*kx
)
1226 if (kx
->f
& KXF_DEAD
)
1229 if (KEY_EXPIRED(now
, kx
->kpriv
->t_exp
)) f
|= 1;
1230 if (KEY_EXPIRED(now
, kx
->kpub
->t_exp
)) f
|= 2;
1233 if (f
& 1) a_warn("KX", "?PEER", kx
->p
, "private-key-expired", A_END
);
1234 if (f
& 2) a_warn("KX", "?PEER", kx
->p
, "public-key-expired", A_END
);
1235 kx
->f
&= ~KXF_PUBKEY
;
1241 /* --- @kx_start@ --- *
1243 * Arguments: @keyexch *kx@ = pointer to key exchange context
1244 * @int forcep@ = nonzero to ignore the quiet timer
1248 * Use: Stimulates a key exchange. If a key exchage is in progress,
1249 * a new challenge is sent (unless the quiet timer forbids
1250 * this); if no exchange is in progress, one is commenced.
1253 void kx_start(keyexch
*kx
, int forcep
)
1255 time_t now
= time(0);
1259 if (forcep
|| !VALIDP(kx
, now
)) {
1262 a_notify("KXSTART", "?PEER", kx
->p
, A_END
);
1267 /* --- @kx_message@ --- *
1269 * Arguments: @keyexch *kx@ = pointer to key exchange context
1270 * @unsigned msg@ = the message code
1271 * @buf *b@ = pointer to buffer containing the packet
1275 * Use: Reads a packet containing key exchange messages and handles
1279 void kx_message(keyexch
*kx
, unsigned msg
, buf
*b
)
1281 struct timeval now
, tv
;
1282 stats
*st
= p_stats(kx
->p
);
1286 gettimeofday(&now
, 0);
1288 if (kx
->f
& KXF_CORK
) {
1289 start(kx
, now
.tv_sec
);
1290 rs_time(&kx
->rs
, &tv
, &now
);
1292 a_notify("KXSTART", "?PEER", kx
->p
, A_END
);
1298 if (!VALIDP(kx
, now
.tv_sec
)) {
1300 start(kx
, now
.tv_sec
);
1302 T( trace(T_KEYEXCH
, "keyexch: processing %s packet from `%s'",
1303 msg
< KX_NMSG ? pkname
[msg
] : "unknown", p_name(kx
->p
)); )
1307 rc
= doprechallenge(kx
, b
);
1310 rc
= dochallenge(kx
, b
);
1313 rc
= doreply(kx
, b
);
1316 rc
= doswitch(kx
, b
);
1319 rc
= doswitchok(kx
, b
);
1322 a_warn("KX", "?PEER", kx
->p
, "unknown-message", "0x%02x", msg
, A_END
);
1335 /* --- @kx_free@ --- *
1337 * Arguments: @keyexch *kx@ = pointer to key exchange context
1341 * Use: Frees everything in a key exchange context.
1344 void kx_free(keyexch
*kx
)
1348 km_unref(kx
->kpriv
);
1351 /* --- @kx_newkeys@ --- *
1353 * Arguments: @keyexch *kx@ = pointer to key exchange context
1357 * Use: Informs the key exchange module that its keys may have
1358 * changed. If fetching the new keys fails, the peer will be
1359 * destroyed, we log messages and struggle along with the old
1363 void kx_newkeys(keyexch
*kx
)
1365 kdata
*kpriv
, *kpub
;
1368 time_t now
= time(0);
1370 T( trace(T_KEYEXCH
, "keyexch: checking new keys for `%s'",
1373 /* --- Find out whether we can use new keys --- *
1375 * Try each available combination of new and old, public and private,
1376 * except both old (which is status quo anyway). The selection is encoded
1377 * in @i@, with bit 0 for the private key and bit 1 for public key; a set
1378 * bit means to use the old value, and a clear bit means to use the new
1381 * This means that we currently prefer `old private and new public' over
1382 * `new private and old public'. I'm not sure which way round this should
1386 for (i
= 0; i
< 3; i
++) {
1388 /* --- Select the keys we're going to examine --- *
1390 * If we're meant to have a new key and don't, then skip this
1394 T( trace(T_KEYEXCH
, "keyexch: checking %s private, %s public",
1395 i
& 1 ?
"old" : "new", i
& 2 ?
"old" : "new"); )
1397 if (i
& 1) kpriv
= kx
->kpriv
;
1398 else if (kx
->kpriv
->kn
->kd
!= kx
->kpriv
) kpriv
= kx
->kpriv
->kn
->kd
;
1400 T( trace(T_KEYEXCH
, "keyexch: private key unchanged, skipping"); )
1404 if (i
& 2) kpub
= kx
->kpub
;
1405 else if (kx
->kpub
->kn
->kd
!= kx
->kpub
) kpub
= kx
->kpub
->kn
->kd
;
1407 T( trace(T_KEYEXCH
, "keyexch: public key unchanged, skipping"); )
1411 /* --- Skip if either key is expired --- *
1413 * We're not going to get far with expired keys, and this simplifies the
1417 if (KEY_EXPIRED(now
, kx
->kpriv
->t_exp
) ||
1418 KEY_EXPIRED(now
, kx
->kpub
->t_exp
)) {
1419 T( trace(T_KEYEXCH
, "keyexch: %s expired, skipping",
1420 !KEY_EXPIRED(now
, kx
->kpriv
->t_exp
) ?
"public key" :
1421 !KEY_EXPIRED(now
, kx
->kpub
->t_exp
) ?
"private key" :
1426 /* --- If the groups don't match then we can't use this pair --- */
1428 if (!km_samealgsp(kpriv
, kpub
)) {
1429 T( trace(T_KEYEXCH
, "keyexch: peer `%s' group mismatch; "
1430 "%s priv `%s' and %s pub `%s'", p_name(kx
->p
),
1431 i
& 1 ?
"old" : "new", km_tag(kx
->kpriv
),
1432 i
& 2 ?
"old" : "new", km_tag(kx
->kpub
)); )
1437 T( trace(T_KEYEXCH
, "keyexch: peer `%s' continuing with old keys",
1441 /* --- We've chosen new keys --- *
1443 * Switch the new ones into place. Neither of the keys we're switching to
1444 * is expired (we checked that above), so we should just crank everything
1447 * A complication arises: we don't really want to force a new key exchange
1448 * unless we have to. If the group is unchanged, and we're currently
1449 * running OK, then we should just let things lie.
1453 switchp
= ((kx
->f
& KXF_DEAD
) ||
1454 kx
->s
!= KXS_SWITCH
||
1455 kpriv
->grp
->ops
!= kx
->kpriv
->grp
->ops
||
1456 !kpriv
->grp
->ops
->samegrpp(kpriv
->grp
, kx
->kpriv
->grp
));
1458 T( trace(T_KEYEXCH
, "keyexch: peer `%s' adopting "
1459 "%s priv `%s' and %s pub `%s'; %sforcing exchange", p_name(kx
->p
),
1460 i
& 1 ?
"old" : "new", km_tag(kx
->kpriv
),
1461 i
& 2 ?
"old" : "new", km_tag(kx
->kpub
),
1462 switchp ?
"" : "not "); )
1464 if (switchp
) stop(kx
);
1465 km_ref(kpriv
); km_unref(kx
->kpriv
); kx
->kpriv
= kpriv
;
1466 km_ref(kpub
); km_unref(kx
->kpub
); kx
->kpub
= kpub
;
1467 kx
->f
|= KXF_PUBKEY
;
1469 T( trace(T_KEYEXCH
, "keyexch: restarting key negotiation with `%s'",
1476 /* --- @kx_init@ --- *
1478 * Arguments: @keyexch *kx@ = pointer to key exchange context
1479 * @peer *p@ = pointer to peer context
1480 * @keyset **ks@ = pointer to keyset list
1481 * @unsigned f@ = various useful flags
1483 * Returns: Zero if OK, nonzero if it failed.
1485 * Use: Initializes a key exchange module. The module currently
1486 * contains no keys, and will attempt to initiate a key
1490 int kx_init(keyexch
*kx
, peer
*p
, keyset
**ks
, unsigned f
)
1492 if ((kx
->kpriv
= km_findpriv(p_privtag(p
))) == 0) goto fail_0
;
1493 if ((kx
->kpub
= km_findpub(p_tag(p
))) == 0) goto fail_1
;
1494 if (!km_samealgsp(kx
->kpriv
, kx
->kpub
)) {
1495 a_warn("KX", "?PEER", p
, "group-mismatch",
1496 "local-private-key", "%s", p_privtag(p
),
1497 "peer-public-key", "%s", p_tag(p
),
1504 kx
->f
= KXF_DEAD
| KXF_PUBKEY
| f
;
1506 if (!(kx
->f
& KXF_CORK
)) {
1509 /* Don't notify here: the ADD message hasn't gone out yet. */
1516 km_unref(kx
->kpriv
);
1521 /*----- That's all, folks -------------------------------------------------*/